1. Field of the Invention
The invention relates to paperboard, corrugated craft and similar cartons and containers made from an integral one piece blank, having contiguous panels that are preliminarily folded and glued such that the carton, container, or tray is manufactured and can be supplied in a knocked-down flat configuration, and is erected into a rectilinear three dimensional form prior to loading with a product or similar contents. In particular the invention concerns a container as described, which is structured as an open-top container or tray, that nests part-way into other similar containers when stacked.
2. Prior Art
Corrugated and paperboard cartons, containers, and trays are cut in required shapes from pieces of flat stock, which usually are folded, and are assembled to form the walls and bottom of a receptacle. Variations are possible in which several integral parts are formed and then assembled using glue, tape, staples or the like. For example, various types of inserts may be used for reinforcement or other purposes such as subdividing the volume of the container into discrete areas or for reinforcing the walls against crushing or displacement.
For convenience in this disclosure, a rectilinear container can be considered to have two pairs of side walls at right angles. The side walls extend perpendicularly upward from a bottom, the opposite side walls being spaced and parallel to one another in opposite pairs. The respective side walls define a front, a back and two opposite end walls, all of which are vertical. A top and bottom are spaced from one another and are horizontal, extending from the upper and lower edges of the side walls. The top is sometimes omitted, or top flaps may be folded inwardly against the inner surface of the sidewalls. The top also may be formed by a separate integral lid member. It will be appreciated that designations such as "top," "bottom," "side" and "end" are used for convenience to distinguish relative positions. Such a container could be in any orientation and could have a "lid" portion which was placed at the position of a side wall or bottom, and otherwise be substantially the same as a more conventional arrangement.
Containers are supplied in a collapsed or knocked-down-flat (KDF) state because storage or handling of empty containers is wasteful of space. KDF containers are partly formed, namely with the necessary parts cut out and preliminarily assembled at certain seams and folds between panels that will form side and end walls, a top and a bottom. Some containers are made without a given wall such as the top, and if they are to be closed off a separately integral lid is provided. The packer erects the container body into a three dimensional shape prior to loading, and in the process finishes the assembly steps that remain. For example, a container may have a number of contiguously adjacent panels cut out from an integral sheet of flat stock, scored and folded at corners between side and end wall panels and between the side and/or end panels and the top and bottom panels, sometimes called flaps. The panels defining the side and end walls can be folded and attached via at least one seam, with the panels knocked-down-flat into a collapsed parallelogram. The container is supplied with the opposite side and end walls collapsed flat against one another. The packer erects the container from a flat configuration into its open-top rectilinear shape, folding the top and bottom flaps perpendicularly inwardly and affixing the flaps to one another and/or to the side or end wall panels.
It is efficient to provide a form of container in which all the container parts are integral extensions of a single piece of flat material, but this also places some constraints on possible structures. Separate parts such as partitions and reinforcing inserts normally involve disadvantageous manual assembly steps that are costly and consume worker time. Assembly steps can be physically taxing for a worker that erects one container after another, and may lead to repetitive motion injuries. Thus it is preferable if containers are as fully formed as possible when they are supplied, nevertheless being knocked-down-flat. It is further preferable if the containers can be made fully erect and functional using the least possible and/or quickest and easiest of manual actions to deploy, load, store, pack and ship the containers.
Self-erecting paperboard and corrugated open-top cartons, containers, and trays are known with their respective walls connected in such a way that one or more of the structural parts of the container is pulled into an erected position as the other parts are erected. For this purpose, bellows folds or gussets can attach adjacent side and end wall panels. The bellows folds are glued on one of two diagonally-attached bellows panels to one of the side or end wall. The other of the side and end wall is folded inward in the KDF configuration. When either of the side and end walls is later pulled into an orientation perpendicular to the bottom (vertical), the bellows folds pull the other of the side and end walls into a perpendicular orientation as well, thus erecting the container.
Containers are routinely stacked vertically to make efficient use of space, and may be reinforced against vertical crushing by employing multiple thicknesses of material for wall panels or by forming columns, for example as in U.S. Pat. No. 5,330,094--Merz. Known structures that are reinforced in this manner are constructed using separate inserts or using a container structure that requires various manual operations to configure and install or erect the reinforcing structure.
Two or more containers are often stacked. Stacked containers are readily carried manually, and are stacked in a storage area or on a pallet or the like to form a compact arrangement for storage or shipping. The stack can have any number of adjacent containers. The individual containers normally can be either in vertical registry or in a staggered overlapping arrangement resembling masonry. Stacking maximizes density for storage, and often enables a group of containers to be handled conveniently as a discrete unit, e.g., using a fork-lift truck or two wheel hand dolly.
Open-top containers can also be stacked. However the containers need to be aligned or structurally arranged such that the vertical walls of the lower container support the upper container. For example, the containers can have side walls with a wide ledge formed at the top to admit a lateral misalignment up to the width of the ledge.
Containers in stacks may be subjected to various vertical and lateral forces. Vertical compression force is applied against lower containers by the weight of upper containers and the product they contain. This vertical force is borne by vertically elongated structural elements in the underlying cartons such as vertical front, back and/or end walls. The structural elements that bear vertical forces on an open-top carton or similar container normally occupy only a limited span of lateral width and/or depth. For example, the vertical forces on many open-top cartons are borne exclusively by their vertical side and end walls. If the stacked open-top cartons remain in registry, then the weight of each upper container is coupled, by the side and end walls of the upper container, to corresponding side and end walls of an underlying container. This is because the side and/or end walls of the upper and lower containers are disposed directly over and under one another.
The present invention provides a site-erected open-top container or carton that is entirely formed from an integral flat blank. The only assembly required is erection from a knocked-down-flat configuration, accomplished by lifting the end walls to perpendicular relative to the back and folding inwardly the flap extensions of the front and back walls to capture extensions of the end walls. The end and side walls taper outwardly relative to vertical when erected, the container forming the inverted frustum of a four sided pyramid (i.e., wider at the top and narrower at the bottom). The end walls have a ledge portion that extends inwardly from an elevation spaced downward from the container rim at the end panel, namely by a glued strip or reinforcing rail. The ledge portion is the top of a self erecting ledge panel that opens from a flattened parallelogram when the end wall is erected to vertical. This structure allows for the nesting of a plurality of containers in a vertical stack, the bottoms of the upper containers being received in the open tops of the lower containers down to the height of the ledge portion.
The container is supplied with substantially all its joints pre-attached, preferably by gluing. The container can be produced automatically in a KDF configuration using a fold-and-glue container production machine, for example as available from Bobst Group, Inc., 146 Harrison Avenue, Roseland, N.J. 07068 (affiliated with Bobst, SA, Lausanne, CH). At the loading site the user need only fold the various wall panels into place, fill the container to produce a stackable unit that is readily handled, stacked on a pallet, or otherwise processed for storage or shipment.